Elemental QuestionsAs lithium-ion battery use increases, so do the concerns related to the fire-safety hazards of these devices. Through a series of research efforts and partnerships, NFPA is analyzing storage and safety issues surrounding the power source fueling hundreds of millions of devices — from iPhones to electric vehicles — worldwide.

NFPA Journal®,March/April 2012

By Fred Durso, Jr.

On a November evening in 2009, residents of Trail, British Columbia, were jolted by explosions that some people thought were part of a fireworks display. The bursts were actually the result of a fire at nearby Toxco Inc., a battery recycling facility. The explosions intensified as the fire ripped through the battery discharge building, and flaming projectiles from a bunker filled with "primary" lithium batteries caused the fire to spread to the adjoining district recycling facility.

YOUTUBE VIDEO INTERVIEW

Senior project manager Andrew Klock gives some insight into the National Highway Traffic Safety Administration's new electric vehicle guidelines and how they can help emergency responders.

The Canadian Broadcasting Corporation reported that the fire was so intense that firefighters could only attempt to contain the blaze for several hours before letting it burn out; lithium is highly reactive to water, and it was feared that attempts to douse the flames might have intensified the blaze. While there were no injuries or deaths, the fire destroyed the battery discharge building. A cause was never identified, but officials speculated that the fire was the result of an internal short in one of the stored batteries.

Incidents like the Toxco fire underscore the flammability and combustibility hazards associated with lithium batteries, which encompass dozens of different chemistries using pure lithium metal or lithium compounds-from the non-rechargeable primary lithium batteries used in industrial applications to the rechargeable lithium-ion cells that power our cameras, mobile phones, and even electric vehicles. Their range of uses is fueling their growing popularity; market projections indicate that the use of lithium-ion batteries, for example, is growing at about 20 percent per year. Cabot, a global performance materials company, reports that battery makers sold about $8 billion of lithium-ion batteries globally last year. By 2020, Cabot says, that number is expected to increase to more than $18 billion. Concerns related to the protection of large quantities of lithium-ion batteries in storage settings against potential fires are expected to rise as more technologies embrace this popular power source.

Among the many industries looking to this emerging power source is the auto industry, which has incorporated lithium technology into its latest crop of electric vehicles (EVs). President Barack Obama has pledged to have a million EVs on U.S. roadways by 2015, a goal supported by U.S. Department of Energy Secretary Steven Chu, who recently said the country has a "good shot" of attaining this target. But the rechargeable lithium-ion battery technology used in these vehicles recently came under scrutiny when a Chevrolet Volt caught fire weeks after a crash test performed as part of a new-vehicle evaluation by the National Highway Traffic Safety Administration (NHTSA). The incident prompted an NHTSA investigation as well as a congressional hearing, where politicians grilled NHTSA and General Motors officials on the vehicle's safety, as well as on the timing of the NHTSA study. (For more on the NHTSA study, see “Crash + Burn.")

As dialogue on battery safety continues, NFPA is working with government agencies, insurers, and car manufacturers to address a national issue of emergency responder and consumer safety, and is offering its input and expertise to address the potential risks. The Fire Protection Research Foundation has initiated a study to identify the hazards, research gaps, and best suppression methods for batteries in storage settings. NFPA's Electric Vehicle Safety Training Project continues to educate the emergency responder and law enforcement communities on the safe handling of these batteries. Staff members have worked with NHTSA to develop guidelines for emergency responders on handling fires involving EVs and hybrid-electric vehicles.

"NFPA is uniquely situated to assist NHTSA and America's responders in looking at the challenges posed by the next generation of vehicles," says Ken Willette, NFPA division manager of Public Fire Protection. "We can draw from our technical expertise to provide best practices when responding to incidents involving these cars. If you add the Foundation's efforts in examining lithium-ion battery storage practices and extinguishing fires involving these battery packs, NFPA was the right choice to support NHTSA's work."

The storage challenge

Much of the current research and safety activity is aimed at lithium-ion batteries, which pack more energy per volume than other rechargeable battery chemistries and are in part responsible for lighter and sleeker designs for consumer electronics. (See “Staying Energized” for a primer on the science of lithium-ion batteries.) The appeal of this battery type extends beyond its size and power, since these power sources are able to maintain the bulk of their charge for months at a time when not in use and typically require minimal maintenance.

But the technology also comes with its own hazards. Late last year, retailer Best Buy and the Consumer Product Safety Commission recalled battery cases made for specific Apple iPhones following incidents of batteries overheating that burned more than a dozen users. In a very different application of the technology, tests on the lithium-ion battery packs in the Chevrolet Volt-General Motors' EV that also relies on a gasoline generator for power once the battery pack is discharged-also resulted in fires, though no incidents of Volt fires on roadways have been documented.

Addressing the potential fire hazards related to this technology, the Fire Protection Research Foundation's Property Insurance Research Group (PIRG) initiated the Lithium-Ion Battery Storage Protection Project last year to address potential fire risks involving these batteries in bulk storage and distribution settings. "What we're seeing is an emerging issue," says Richard Gallagher, line of business director-property for Zurich Services Corporation Risk Engineering and a PIRG member. "We realized that we're going to see warehouses filled with these batteries, but we really don't know how to protect them. Nowhere is there guidance to direct a building owner on how to protect this commodity."

The project's first phase was a literature review commissioned last year by the Foundation that identified these gaps in fire protection and assessed battery hazards. Among the hazard issues addressed in the final report, Lithium-Ion Batteries Hazard and Use Assessment, was the battery's makeup, particularly its high energy density and flammable solvent that aids ion movement in battery cells during charging. The report also identified the rare, yet potentially dangerous, circumstances leading to battery failure, including poor cell design or defects leading to short circuits, cell manufacturing flaws, external abuse of cells, and charging inadequacies. The rapid self-heating of a cell, known as "thermal runaway," is what the report terms an "energetic failure" that may cause the electrolyte to combust, potentially leading to a fire spreading to other battery cells or venting of potentially flammable vapors.

While there have been numerous studies conducted on small quantities of cells and small battery packs, little is known about the fire hazards of thermal runaway reactions, how these batteries burn in large quantities, or what suppression tactics are most effective. "This is a commodity that's become ubiquitous, and the fact that it's become ubiquitous before we've resolved these kinds of issues tell how well [lithium-ion batteries] work," says Celina Mikolajczak, senior managing engineer with Exponent, the engineering and scientific consulting firm that developed the research report for the Foundation. "They have been in the marketplace for about 20 years, originally in small volumes. As more cells are being shipped and more people use them, we certainly want to be aware of the associated risks, especially as bigger batteries are developed and we contemplate greener technologies."

PIRG met last August at the Foundation's Lithium-Ion Battery Storage Hazard Assessment Workshop in Baltimore to discuss findings from the Foundation's report and remaining gaps in fire hazard and suppression research. The workshop's "general battery storage" subgroup agreed that full-scale fire tests in these settings would determine the appropriate containment methods.

Heeding this advice, PIRG will begin testing this year as part of the second phase of its research project, which also includes determining the appropriate fire protection commodity classification for lithium-ion batteries. Exponent has already identified various commodity types and their challenges relative to bulk storage protection. PIRG has condensed its research list to two particular commodity types: small-format battery packs, and cells packed in large modules that when combined form EV batteries. PIRG will share the commodity classifications and testing results with NFPA 13, Installation of Sprinkler Systems, technical committees in order to aid the development of provisions related to lithium-ion battery storage. "Once the nature of the commodity is understood, the next step is to identify compatible fire extinguishing agents and design guidelines that the NFPA 13 committees can use to fill the current voids," says Gallagher.

The EV challengeLithium-ion car batteries received their fair share of attention over the past year. NHTSA, which occasionally assesses vehicles that incorporate new technology, initiated a series of tests on EVs last year. According to the agency's Chevrolet Volt Battery Incident Overview Report published in January, a crash test in May involving the Volt resulted in the leakage of battery coolant, damage to some of the battery's cells, and an electric short that precipitated a fire three weeks after the crash. During another round of tests in November, batteries began to smoke and emit sparks, while another caught fire a week after the tests.

While NHTSA isn't aware of any roadway crashes resulting in EV battery fires, it opened a defect investigation on the Volt in late November to further analyze the findings. A month later, GM proposed several modifications to the Volt, including the strengthening of the car's structure to further protect the battery pack during a collision and the addition of a sensor to monitor battery coolant levels. The upgrades will be applied to vehicles in production, as well as to the more than 8,000 Volts already on the road.

Also in November, NHTSA contacted NFPA to help assemble a series of interim guidelines for emergency responders, tow truck operators, consumers, and storage facilities to consider in the event of an EV or hybrid-electric vehicle fire. Staff members and consultants with NFPA's Electric Vehicle Safety Training Project and Public Fire Protection Division, who are well versed on handling various hazardous materials and response procedures, collaborated for the new project. NFPA is incorporating the interim guidelines into its EV training project, which instructs emergency responders on the growing fleet of EVs and related hazards through a series of online and classroom trainings.

"I'd compare NFPA's role in developing the interim guidelines to a fire ground commander calling in a specialty team to assist with a challenging situation," says NFPA's Willette. "NHSTA called us to provide technical guidance and insight into the development of the interim guidelines. The NFPA team responded, with all members focusing on their tasks until the mission was accomplished." With that input, Willette says, NHSTA was able to draft the interim guidelines.

Following the creation of the guidelines and structural safeguards for the Volt, NHTSA concluded its investigation in January. "NHTSA does not believe that the Chevy Volt or other electric vehicles pose a greater risk of fire than gasoline-powered vehicles," the agency said in a statement. (NFPA statistics indicate that in 2010 there were roughly 184,000 highway vehicle fires, nearly all of them in gasoline-powered vehicles, which resulted in 285 deaths.) "The agency expects this guidance will help inform the ongoing work by NFPA, the Department of Energy, and vehicle manufacturers to educate the emergency response community, law enforcement officers, and others about electric vehicles."

The manner in which NHTSA responded to the series of fires involving the Volt perplexed some politicians. A subcommittee of the House Oversight and Government Reform Committee held a hearing in January with NHTSA Administrator David Strickland, along with Dan Akerson, General Motor's chairman and chief executive officer, to question NHTSA on why it waited six months after the initial battery fire to launch an official investigation. The proceedings were at times acrimonious. "Your agency dropped the ball on this," U.S. Rep. Mike Kelly, a Pennsylvania Republican and committee member, said to Strickland at the hearing, according to the Grand Rapids Press. "For me, it comes down to taxpayer dollars being used to subsidize a product that this administration wants to go forward."

Strickland acknowledged the safety of the Volt and pointed out that there had been no on-the-road incidences of battery fires. He also testified that engineers used that time to meticulously analyze the cause of the fires. Had there been a public safety concern, Strickland said, NHTSA would have brought the issue to light sooner.

Gregory Cade, NFPA division director of Government Affairs, attended the hearing and noted that both Strickland and Akerson complimented NFPA for its involvement in developing the interim guidelines and on its collaboration with GM on aspects of NFPA's Electric Vehicle Safety Training Project. "The dilemma is that GM is only one carmaker using one battery technology," says Cade. "We've got to continue to reach out to other car and battery manufacturers. They're not all using the same technology."

NFPA has also continued expanding its EV training to other interested parties. The Department of Energy, which had initially awarded NFPA a $4.4 million grant in 2010 for its EV training project, recently extended participation to EMS and law enforcement officials. More than 15,000 people have already registered for an online training course featuring electrical and safety information on the Volt.

The course complements the project's "train the trainer" classroom courses attended by about 800 fire service professionals in 20 states. Anticipated for release this year is a reference guide that instructs emergency responders on identifying all makes and models of hybrid cars and EVs as well as how to safely respond to the vehicles in an emergency.

The training developments underscore NFPA's role as the authority on EV battery safety, says Andrew Klock, senior project manager for the EV Safety Training Project. "The training is exceeding our expectations," he says. "The attendance across the country has been much better than we anticipated. We thought we would have 45 fire service trainers in each state taking the course. In many states, we're pushing over 100. The EV Safety Training Project website is also becoming the place where the emergency responder community is getting their hybrid and EV safety information."

Looking ahead, the Foundation is partnering with the automotive industry and the Department of Energy (DOE) this year to develop best practices for the safe handling and disposal of damaged automotive batteries by emergency responders. The project is yet another aspect of the larger effort to assess and address the fire protection strategies of this rapidly emerging technology.

"EV battery safety represents a special challenge as this technology is in a rapid state of evolution," says Kathleen Almand, the Foundation's executive director. "Both NFPA and the Foundation have been proactively addressing many new energy-related technologies, from solar panels, to biofuel safety, to electric safety aspects of plug-in EVs to ensure that NFPA standards are appropriately addressing all of these emerging issues."

An EV battery damaged in a crash test started a fire that destroyed four vehicles at a test facility in Wisconsin. (Photo: NHSTA)

As part of its New Car Assessment Program (NCAP), NHTSA conducted four side-pole crash tests of the Chevrolet Volt in 2011 to evaluate the vehicle’s crashworthiness and occupant protection. All of the tested vehicles met compliance test requirements and were favorably rated for the NCAP program. Based on its performance, the Volt received an NHTSA five-star rating for both frontal and side-impact vehicle crashworthiness and occupant protection.

A side-pole crash test of a Chevrolet Volt was conducted on May 12, 2011, at MGA Research, a test facility in Wisconsin. On June 6, 2011, MGA Research personnel notified NHTSA that a fire event had occurred over the previous weekend and had been discovered by laboratory staffers that morning. The laboratory provided details of the vehicles involved in the event, which included the Chevrolet Volt that had been subjected to an NCAP pole test three weeks earlier.

After informing NHTSA about the fire, MGA notified the local fire authorities, who performed an initial scene investigation that focused on identifying possible arson issues. NHTSA contracted with a battery and fire expert, Hughes Associates, to investigate the origin and cause of the fire. The initial forensic inspection was conducted June 13–14 at the MGA facility. In July 2011, Hughes Associates’ preliminary findings indicated that the fire incident at MGA most likely originated in the Chevrolet Volt.

This preliminary finding triggered further investigation. The vehicle, along with the fire-damaged lithium-ion propulsion battery, was shipped to NHTSA’s Vehicle Research and Test Center in East Liberty, Ohio. Hughes Associates, NHTSA, and General Motors (GM) representatives conducted a forensic inspection and battery teardown. The inspection of the crash damage to the Volt revealed that the transverse stiffener located under the driver’s seat had penetrated the tunnel section of the battery compartment, damaged the lithium-ion battery, and ruptured the battery’s liquid cooling system. Review of the crash test photographs and video confirmed that coolant had leaked from the battery compartment. Hughes Associates concluded that damage to some of the Volt’s battery pack cells and electric shorting precipitated the fire.

In September 2011, NHTSA performed a fifth side-pole NCAP crash test on a Chevrolet Volt at the MGA facility. The objective was to observe any battery cell damage, shorting, battery coolant system rupture, or post-crash battery fire. The test vehicle was fitted with additional cameras and equipment to monitor post-crash events. This test resulted in no intrusion into the battery compartment, no cell damage or shorting, no leakage of coolant, and no post-impact fire. The vehicle was monitored for three weeks after the crash.

Six additional tests were performed on Volt lithium-ion battery packs to isolate potential factors involved in the MGA vehicle fire. Of the six tests, two batteries caught fire — one six days after the test, the other a week after testing. Another experienced a short arcing event with sparks and flames, one battery showed signs of heating at the connector, and another battery showed no test-related activity other than a slow discharge of one cell group. The sixth battery was inadvertently consumed by one of the batteries that caught fire. Despite the fires, NHTSA was unable to replicate the specifics of the MGA fire event in either the battery component testing or the full-scale vehicle tests and is not aware of any real-world post-crash fires involving an EV battery cell venting event.

In November 2011, NHTSA opened a defect investigation on the Chevrolet Volt. GM proposed a potential change (field fix) to mitigate intrusion of the transverse stiffener into the battery. NHTSA observed the installation of the proposed reinforcement into a 2012 production Chevrolet Volt, and the vehicle was shipped to MGA Research where an NCAP-style side-pole test was performed in December. The vehicle was monitored for three weeks. There was no intrusion into the battery compartment, no leakage of coolant, and no post-impact fire observed.

In November 2011, NHTSA also began working with NFPA to assist first and second responders in identifying vehicles powered by lithium-ion and other lithium-type batteries in taking appropriate steps in handling these batteries following a crash. NHTSA has also been working with vehicle manufacturers to develop appropriate post-crash protocols for dealing with lithium-ion battery powered vehicles.

SIDEBARFrench ConnectionUpcoming seminar underscores global impact of European research on lithium-ion batteries

To truly understand the hazardous nature of lithium-ion batteries, and to develop corresponding safety measures against potential threats, the batteries must undergo a series of destructive tests.

In operation since 2010, the testing facility’s sole purpose is to examine the ramifications of battery abuse. The French National Institute for Industrial Environment and Risks (INERIS), which addresses risks impacting life and property safety through studies and research programs, developed STEEVE in order to take a close look at lithium-ion batteries and to try to determine what has led to a smattering of international battery fires. Its latest research will be discussed during the High Challenge Storage Protection Seminar in Paris on June 27. Presented by the Fire Protection Research Foundation, the seminar addresses high-hazard commodities in storage settings and new approaches to fire protection.

While INERIS has yet to initiate research on lithium-ion batteries in storage settings, it has begun researching the life cycle of these devices and has identified potential hazardous scenarios along the way. The session at the Foundation seminar will identify the scenarios, including possible incidents involving the toxic components of these batteries, and prevention measures that optimize building protection.

“In a [battery] recycling plant, you’ll never know the state of health of the batteries,” says Guy Marlair, technical advisor and research scientist with INERIS. “They may be very close to the thermal runaway process [rapid self-heating of battery cells], or very far from that. It’s difficult to have a clear idea. The way you will develop prevention and protection measures in a recycling facility will have to be different than warehouses storing new cells and batteries.”

A technical panelist for the Foundation’s Lithium-Ion Battery Storage Protection Project, Marlair says he plans to share current and future research findings for the good of the project. “This project is quite timely,” he says. “We have to consolidate the research effort. We should concentrate on collecting all pieces of new information to achieve a satisfactory level of safety for the storage of these batteries. All of these different types of defects will need to be analyzed to ensure protection.”

For more information on the Research Foundation’s High Challenge Storage Protection Seminar, visit nfpa.org/foundation.

A lithium-ion battery’s ability to provide considerable amounts of energy using lighter materials than its competitors has made this technology a popular option for consumer electronics and the growing electric vehicle industry. Here’s a simplified look at the science responsible for powering many of today’s gadgets.

Salar de Uyuni, in Bolivia, holds the world's largest reserve of lithium. (Photo: Corbis)

Lithium in its purest form — a silvery-white metallic element — is not found in lithium-ion cells. Rather, a chemical compound containing lithium (in some cases, lithium cobalt oxide) is used. The term “lithium-ion” refers to the positively charged atoms responsible for the battery’s charging and discharging. A lithium-ion battery’s metallic case contains a lithium-ion cell consisting of anodes (negative electrodes) that are commonly composed of lightweight elements, such as carbon, and cathodes (positive electrodes), a ceramic material made from the lithium cobalt oxide or other materials. The cathodes and anodes are placed onto individual copper or aluminum foils, separated by a porous piece of film, and submerged in an organic solvent known as an electrolyte. As the battery charges, the electrolyte aids the lithium ions (charged atoms created by the lithium salt in the electrolyte) that move through the film from the cathode to the anode. The direction of the ions is reversed during discharge, creating a flow of an electrical current. The batteries produce a higher voltage and can be recharged for hundreds of cycles, making these devices an increasingly popular power source. Cell phones, for example, use single-cell lithium-ion batteries, while notebook computers and other larger devices use multi-cell batteries.

Since lithium-ion batteries are sensitive to extreme temperatures, the battery pack or individual cell typically have a range of overcharge protection devices. Whereas comparable battery technologies use a water-based solvent as its electrolyte, lithium-ion batteries use a flammable solvent to perpetuate ion movement. Research has indicated that the device’s high energy density and flammable solvent pose risks and challenges related to the storage and handling of these batteries.